The air-conditioning or climate control, i.e. the ventilation with simultaneous heating or cooling, of aircraft freight compartments is conventionally achieved by blowing temperature regulated supply air into the freight compartment at several distributed locations through respective air outlets. After traversing through the cargo or freight compartment, this air exits the freight compartment through respective exhaust openings. A particular air flow pattern or profile through the space is achieved by appropriately arranging the air outlets and the air exhaust openings in the freight compartment.
In this context, the spatial temperature distribution is to be tuned or adjusted dependent on the existing or prevailing environmental conditions. To achieve this, a freight compartment temperature control unit (which is particularly a closed loop control or regulating unit) is provided in the aircraft to regulate the air temperature of the supply air being blown or injected into the freight compartment dependent upon the interior temperature of the freight compartment and as necessary in view of the respective existing surrounding environmental conditions. This freight compartment interior temperature corresponds to a representative interior temperature of the overall freight compartment. In this context, the positioning of a temperature sensor within the freight compartment is strictly prescribed due to the above described temperature distribution.
Furthermore, a separate reduced pressure source such as a suction blower must be provided, or the available exhaust air flow out of the freight compartment must be used to provide a forced or positive ventilation of the temperature sensor. However, in actual practice, varying loading configurations of different freight items within the freight compartment in successive flights lead to varying spatial air flow patterns through the freight compartment, which in turn cause considerable deviations between the measured freight compartment temperature and the actual or true representative interior temperature of the overall freight compartment.
Conventionally, the air within the aircraft freight compartment is monitored for the presence of smoke, separately from the temperature monitoring, for the purpose of detecting fires or the like. More specifically, smoke detectors and smoke alarms are positioned freely or independently within the freight compartment or are located remotely and simply provided with freight compartment air through a reduced pressure system, for example through a blower, so as to indicate the presence of smoke by releasing an alarm. Various aircraft and flight regulations require that the smoke alarms provide an acoustic warning or alarm signal within one minute after the first evolution of smoke. Of course, the distribution of smoke through the freight compartment after its initial evolution, and emanating from its site of evolution, is determined by the above described spatial air flow pattern through the freight compartment. Thus, in order to fulfill the above described regulations, the smoke alarms must be positioned in the freight compartment so that it is ensured that smoke arising at any location within the freight compartment will reach at least one of the smoke detectors or smoke alarms within the prescribed interval of one minute.
Since the spatial air flow pattern through the freight compartment will vary dependent upon the varying loading configurations, as described above, the functioning of the smoke detectors or alarms is also subject to a measurement error or triggering delay that is dependent upon the particular loading configuration at any given time. In order to minimize this measurement error, or to maintain this measurement error within acceptable limits, for all possible loading configurations, it would be necessary to carry out a series of experiments with different loading configurations and resultant different air flow patterns, whereby the experimental results could then be used to reach a compromise between the plurality of different configurations and the resultant measurement errors in different cases.
There is no known solution or suggestion for overcoming the above described problems involved in the constant monitoring of the temperature and of the possible presence of smoke in the air within closed spaces or compartments in the fuselage of an aircraft, and particularly the freight compartments. Especially, the known art provides no suggestions for minimizing or achieving the smallest possible measurement errors or variations, of which the monitoring results are completely or substantially independent of the particular loading configuration or cabin layout and passenger loading in the freight or passenger compartments of an aircraft. Moreover, the prior art has not provided any manner of increasing the reliability of the temperature regulation and smoke detection in such freight and/or passenger compartments in an aircraft.